Photocurable resin composition and optical adhesive

Abstract

The present invention provides a photocurable resin composition that can maintain excellent adhesiveness even under high temperature and high humidity and that can be applied as a thin film when adhering adherends to each other. The photocurable resin composition of the present invention contains a (meth)acrylic polymerizable compound (A), a photopolymerization initiator (B), a silane coupling agent (C) having an SP value of less than 17.5, and a silane coupling agent (D) having an SP value of 17.5 or more and can therefore firmly adhere and integrate adherends to each other even under high temperature and high humidity.

Description

[Technical Field]

[0001] The present invention relates to a photocurable resin composition and an optical adhesive. [Background technology]

[0002] Photocurable resin compositions have been used for bonding adherends such as glass and synthetic resins. In the optical field, for bonding lenses and prisms, the thickness of the coating film of the photocurable resin composition must be reduced to about several micrometers.

[0003] Furthermore, in recent years, the use of optical lenses in automotive applications has increased with the spread of automated driving and safe driving management systems, and there is a demand for reliable lenses that do not lose adhesion even in the high-temperature, high-humidity environment inside an automobile.

[0004] As such a curable resin composition, Patent Document 1 discloses an adhesive composition for electronic components, which contains a polymerizable compound (A) excluding a silane coupling agent (C) and / or a phosphate group-containing polymerizable monomer (D), a photopolymerization initiator (B), and the silane coupling agent (C) and / or a phosphate group-containing polymerizable monomer (D) represented by a specific structural formula. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-153957 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the adhesive composition for electronic components of Patent Document 1 has problems in that its adhesiveness decreases under high temperature and high humidity conditions, and its reliability is low under high temperature and high humidity conditions. Therefore, there is a demand for a curable resin composition that has excellent adhesiveness under high temperature and high humidity conditions.

[0007] The present invention provides a photocurable resin composition that can maintain excellent adhesive properties even under high temperature and high humidity conditions. [Means for solving the problem]

[0008] The photocurable resin composition of the present invention is characterized by containing a (meth)acrylic polymerizable compound (A), a photopolymerization initiator (B), a silane coupling agent (C) having an SP value of less than 17.5, and a silane coupling agent (D) having an SP value of 17.5 or more.

[0009] The optical adhesive of the present invention is characterized by containing the above-mentioned photocurable resin composition. [Effects of the Invention]

[0010] The photocurable resin composition of the present invention can firmly bond and integrate adherends together even under high temperature and high humidity conditions. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic side view showing the procedure for measuring adhesive strength. [Figure 2] FIG. 2 is a schematic plan view showing the procedure for measuring adhesive strength. DETAILED DESCRIPTION OF THE INVENTION

[0012] The photocurable resin composition of the present invention contains a (meth)acrylic polymerizable compound (A), a photopolymerization initiator (B), a silane coupling agent (C) having an SP value of less than 17.5, and a silane coupling agent (D) having an SP value of 17.5 or more.

[0013] [(Meth)acrylic polymerizable compound (A)] The photocurable resin composition contains a (meth)acrylic polymerizable compound (A). The (meth)acrylic polymerizable compound (A) has a radically polymerizable unsaturated bond (e.g., an ethylenically unsaturated double bond) in the molecule.

[0014] The (meth)acrylic polymerizable compound (A) is not particularly limited, and examples thereof include monofunctional (meth)acrylates, polyfunctional (meth)acrylates, acrylic acid, and methacrylic acid. (Meth)acrylate refers to acrylate or methacrylate. The (meth)acrylic polymerizable compound (A) does not contain a silicon atom (Si) in the molecule. (Meth)acrylate refers to a compound having an acrylate structure (-COO-) produced by the reaction of a carboxyl group (-COOH) and a hydroxyl group (-OH).

[0015] In the present invention, the (meth)acrylic polymerizable compound refers to a polymerizable compound having an acryloyl group [formula (4)] or a methacryloyl group [formula (5)] in the molecule. In formulas (4) and (5), *4 and *5 are bonding bonds and represent single bonds.

[0016] [ka]

[0017] The (meth)acrylic polymerizable compound (A) is preferably a monofunctional methacrylate or a polyfunctional methacrylate, since it can reduce the cure shrinkage of the polymer obtained by curing the photocurable resin composition, thereby improving the adhesion between the resulting polymer and an adherend under high temperature and high humidity conditions. The (meth)acrylic polymerizable compound (A) may be used alone or in combination of two or more.

[0018] The (meth)acrylic polymerizable compound (A) preferably contains a monofunctional (meth)acrylate, since this improves the adhesiveness of the cured product (polymer) of the photocurable resin composition to the adherend. The (meth)acrylic polymerizable compound (A) preferably contains a monofunctional (meth)acrylate and a polyfunctional (meth)acrylate, since this improves the adhesiveness of the cured product (polymer) of the photocurable resin composition under high temperature and high humidity conditions. The (meth)acrylic polymerizable compound (A) preferably contains a monofunctional (meth)acrylate, (meth)acrylic acid, and a polyfunctional (meth)acrylate, since this improves the adhesiveness of the cured product (polymer) of the photocurable resin composition under high temperature and high humidity conditions. The monofunctional (meth)acrylate has only one radically polymerizable unsaturated bond (e.g., an ethylenically unsaturated double bond) in the molecule. The polyfunctional (meth)acrylate has multiple radically polymerizable unsaturated bonds (e.g., an ethylenically unsaturated double bond) in the molecule. (Meth)acrylic acid means acrylic acid or methacrylic acid.

[0019] The content of (meth)acrylate in the (meth)acrylic polymerizable compound (A) is preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, and more preferably 85% by mass or more, since the adhesiveness of the cured product (polymer) of the photocurable resin composition under high temperature and high humidity conditions is improved. The content of (meth)acrylate in the (meth)acrylic polymerizable compound (A) is preferably 95% by mass or less, more preferably 93% by mass or less, and more preferably 90% by mass or less, since the adhesiveness of the cured product (polymer) of the photocurable resin composition to an adherend is improved.

[0020] The content of the monofunctional (meth)acrylate in the (meth)acrylic polymerizable compound (A) is preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 65% ​​by mass or more, and more preferably 70% by mass or more, since the adhesiveness of the cured product (polymer) of the photocurable resin composition to an adherend is improved. The content of the monofunctional (meth)acrylate in the (meth)acrylic polymerizable compound (A) is preferably 90% by mass or less, more preferably 85% by mass or less, and more preferably 80% by mass or less, since the adhesiveness of the cured product (polymer) of the photocurable resin composition under high temperature and high humidity conditions is improved.

[0021] The content of (meth)acrylic acid in the (meth)acrylic polymerizable compound (A) is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, since the adhesiveness of the cured product (polymer) of the photocurable resin composition to an adherend is improved. The content of (meth)acrylic acid in the (meth)acrylic polymerizable compound (A) is preferably 20% by mass or less, more preferably 15% by mass or less, since the adhesiveness of the cured product (polymer) of the photocurable resin composition under high temperature and high humidity conditions is improved.

[0022] The content of the polyfunctional (meth)acrylate in the (meth)acrylic polymerizable compound (A) is preferably 5% by mass or more, more preferably 10% by mass or more, and more preferably 15% by mass or more, since the adhesiveness of the cured product of the photocurable resin composition under high temperature and high humidity conditions is improved by imparting cohesive strength to the cured product of the photocurable resin composition. The content of the polyfunctional (meth)acrylate in the (meth)acrylic polymerizable compound (A) is preferably 70% by mass or less, more preferably 65% ​​by mass or less, more preferably 60% by mass or less, more preferably 50% by mass or less, more preferably 40% by mass or less, more preferably 35% by mass or less, more preferably 30% by mass or less, and more preferably 25% by mass or less, since the adhesiveness of the cured product of the photocurable resin composition to an adherend is improved by imparting an appropriate crosslink density to the cured product (polymer) of the photocurable resin composition.

[0023] The monofunctional (meth)acrylate is not particularly limited, and examples thereof include monofunctional alkyl (meth)acrylates, monofunctional (meth)acrylates having a saturated aliphatic ring structure, monofunctional (meth)acrylates having an aromatic ring, and monofunctional (meth)acrylates having a polar group. Monofunctional alkyl (meth)acrylates, monofunctional (meth)acrylates having a saturated aliphatic ring structure, and monofunctional (meth)acrylates having an aromatic ring do not have a polar group. Examples of polar groups include a carboxyl group (-COOH), a hydroxyl group (-OH), a phosphonic acid group [-P(=O)(OH)2], a phosphate group [-OP(=O)(OH)2], and a functional group represented by formula (6). In formula (6), *6 and *7 represent bonds and single bonds.

[0024] [ka]

[0025] Examples of monofunctional alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)methacrylate, stearyl (meth)acrylate, etc. The alkyl (meth)acrylates may be used alone or in combination of two or more.

[0026] In the present invention, an alkyl group refers to an atomic group remaining after removing one hydrogen atom from an aliphatic saturated hydrocarbon. The hydrogen atoms of the alkyl group are not replaced by other atoms or atomic groups. The alkyl group may be either linear or branched.

[0027] As the monofunctional (meth)acrylate having saturated aliphatic ring structure, for example, can be enumerated isobornyl (meth)acrylate, norbornyl (meth)acrylate, tricyclononyl (meth)acrylate, tricyclodecyl (meth)acrylate, tetracyclodecyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, 3,5,5-trimethylcyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, adamantyl (meth)acrylate etc., and preferably dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate.In addition, the (meth)acrylate having saturated aliphatic ring structure can be used alone or two or more can be used together.

[0028] Examples of the monofunctional (meth)acrylate having an aromatic ring include phenoxyalkyl acrylates such as phenoxyethyl acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, and dicyclopentenyl (meth)acrylate, among which phenoxyalkyl acrylates are preferred, and phenoxyethyl acrylate is more preferred. The (meth)acrylates having an aromatic ring may be used alone or in combination of two or more.

[0029] In the monofunctional (meth)acrylate having a polar group, examples of the polar group include a carboxyl group (-COOH), a hydroxyl group (-OH), a phosphonic acid group [-P(=O)(OH)2], a phosphate group [-OP(=O)(OH)2], and a functional group represented by formula (6), of which a hydroxyl group, a phosphate group, and a functional group represented by formula (6) are preferred. In formula (6), *6 and *7 represent bonds and single bonds.

[0030] [ka]

[0031] Examples of monofunctional (meth)acrylates having a polar group include monofunctional alkyl (meth)acrylates in which the hydrogen of an alkyl group is substituted with a polar group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-hydroxybutyl (meth)acrylate; hydroxy monofunctional (meth)acrylates such as polyethylene glycol mono(meth)acrylate; and 2-(meth)acryloyloxyethyl acid phosphate, with 2-hydroxyethyl (meth)acrylate being preferred. The monofunctional (meth)acrylates having a polar group may be used alone or in combination of two or more. (Meth)acryloxy refers to acryloxy or methacryloxy.

[0032] The content of the monofunctional alkyl (meth)acrylate in the (meth)acrylic polymerizable compound (A) is preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 55% by mass or more, more preferably 60% by mass or more, and more preferably 70% by mass or more, since the adhesiveness of the cured product (polymer) of the photocurable resin composition to an adherend is improved. The content of the monofunctional alkyl (meth)acrylate in the (meth)acrylic polymerizable compound (A) is preferably 95% by mass or less, more preferably 90% by mass or less, and more preferably 85% by mass or less, since the adhesiveness of the cured product (polymer) of the photocurable resin composition under high temperature and high humidity conditions is improved.

[0033] In the (meth)acrylic polymerizable compound (A), the content of the monofunctional (meth)acrylate having a saturated aliphatic ring structure is preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 63% by mass or more, and more preferably 66% by mass or more. In the (meth)acrylic polymerizable compound (A), the content of the monofunctional (meth)acrylate having a saturated aliphatic ring structure is preferably 90% by mass or less, more preferably 85% by mass or less, and more preferably 80% by mass or less. When the content of the monofunctional (meth)acrylate having a saturated aliphatic ring structure is 20% by mass or more, cohesion is imparted to the cured product (polymer) of the photocurable resin composition, thereby improving the adhesiveness of the photocurable resin composition under high temperature and high humidity conditions. When the content of the monofunctional (meth)acrylate having a saturated aliphatic ring structure is 90% by mass or less, the adhesiveness of the photocurable resin composition under high temperature and high humidity conditions is improved.

[0034] In the (meth)acrylic polymerizable compound (A), the content of the monofunctional (meth)acrylate having a polar group is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and more preferably 0.3% by mass or more. In the (meth)acrylic polymerizable compound (A), the content of the monofunctional (meth)acrylate having a polar group is preferably 20% by mass or less, more preferably 15% by mass or less, more preferably 12% by mass or less, more preferably 10% by mass or less, more preferably 8% by mass or less, and more preferably 6% by mass or less. When the content of the monofunctional (meth)acrylate having a polar group is 0.1% by mass or more, the adhesiveness of the cured product of the photocurable resin composition to the adherend is improved due to intermolecular forces with the polar group present on the surface of the adherend. When the content of the monofunctional (meth)acrylate having a polar group is 20% by mass or less, swelling of the cured product of the photocurable resin composition due to moisture absorption is reduced, and the adhesiveness of the photocurable resin composition to the adherend under high temperature and high humidity conditions is improved.

[0035] The polyfunctional (meth)acrylate is not particularly limited, but a bifunctional (meth)acrylate is preferred because it improves the adhesiveness of the cured product (polymer) of the photocurable resin composition under high temperature and high humidity conditions. The content of the bifunctional (meth)acrylate in the polyfunctional (meth)acrylate is preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, more preferably 99% by mass or more, and more preferably 100% by mass.

[0036] Examples of polyfunctional (meth)acrylates include polyfunctional (meth)acrylates that do not have a polar group, such as 1,6-hexanediol (meth)acrylate, 1-((meth)acryloxy)-3-((meth)acryloxy)-2-propanol, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, and hydroxypivalic acid neopentyl glycol (meth)acrylic acid adduct, and polyfunctional (meth)acrylates that have a polar group, such as bis(2-(meth)acryloxyethyl) acid phosphate, pentaerythritol tri(meth)acrylate, and dipentaerythritol penta(meth)acrylate, of which 1,6-hexanediol (meth)acrylate, triethylene glycol di(meth)acrylate, and bis(2-(meth)acryloxyethyl) acid phosphate are preferred. The polyfunctional (meth)acrylates may be used alone or in combination of two or more.

[0037] In the polyfunctional (meth)acrylate having a polar group, examples of the polar group include a carboxyl group (-COOH), a hydroxyl group (-OH), a phosphonic acid group [-P(=O)(OH)2], a phosphate group [-OP(=O)(OH)2], and a functional group represented by formula (6), of which a hydroxyl group, a phosphate group, and a functional group represented by formula (6) are preferred. In formula (6), *6 and *7 represent bonds and single bonds.

[0038] [ka]

[0039] The polyfunctional (meth)acrylate preferably contains a (meth)acrylic oligomer having an acryloxy group [formula (1)] or a methacryloxy group [formula (2)] at both ends of its main chain. When the (meth)acrylic oligomer is contained, the cured product of the photocurable resin composition has excellent adhesiveness under high temperature and high humidity conditions. In the present invention, the main chain refers to the longest chain in the molecule. The length of the chain is determined based on the number of atoms directly constituting the chain; the greater the number of atoms, the longer the chain length.

[0040] The main chain of the (meth)acrylic oligomer is not particularly limited, but is preferably a main chain containing at least one skeleton selected from the group consisting of a polyurethane skeleton, a polyisoprene skeleton, and a polybutadiene skeleton. The main chain of the (meth)acrylic oligomer preferably contains a polyurethane skeleton, since the cured product of the photocurable resin composition exhibits superior adhesiveness under high temperature and high humidity conditions.

[0041] The (meth)acrylic oligomer preferably contains a polyester skeleton, a polycarbonate skeleton, or a polyether skeleton in the main chain, more preferably a polyester skeleton or a polycarbonate skeleton, and even more preferably a polyester skeleton, because the cured product of the photocurable resin composition exhibits superior adhesiveness under high temperature and high humidity conditions.

[0042] Since the cured product of the photocurable resin composition exhibits superior adhesive properties under high temperature and high humidity conditions, the (meth)acrylic oligomer preferably has a main chain having a polyurethane skeleton and a polyester skeleton, or a polyurethane skeleton and a polycarbonate skeleton. A (meth)acrylic oligomer having a polyurethane skeleton and a polyester skeleton in the main chain is commercially available, for example, from Nippon Kayaku Co., Ltd. under the trade name "UX-4101." A (meth)acrylic oligomer having a polyurethane skeleton and a polycarbonate skeleton in the main chain is commercially available, for example, from Negami Chemical Industrial Co., Ltd. under the trade name "UN-9000PEP."

[0043] The weight-average molecular weight of the (meth)acrylic oligomer is preferably 1,000 or more, more preferably 2,000 or more, and more preferably 3,000 or more. The weight-average molecular weight of the (meth)acrylic oligomer is preferably 100,000 or less, more preferably 50,000 or less, more preferably 30,000 or less, more preferably 20,000 or less, more preferably 15,000 or less, more preferably 13,000 or less, more preferably 12,000 or less, more preferably 11,000 or less, more preferably 10,000 or less, and more preferably 8,000 or less. When the weight-average molecular weight of the (meth)acrylic oligomer is 1,000 or more, the cured product of the photocurable resin composition exhibits superior adhesiveness under high temperature and high humidity conditions. When the weight-average molecular weight of the (meth)acrylic oligomer is 100,000 or less, the cured product of the photocurable resin composition exhibits superior adhesiveness under high temperature and high humidity conditions.

[0044] In the present invention, the weight average molecular weight of the (meth)acrylic oligomer means a value calculated in terms of polystyrene measured by GPC (gel permeation chromatography).

[0045] The weight average molecular weight of the (meth)acrylic oligomer can be measured, for example, using the following measuring device and under the following measuring conditions. Measurement device: Waters product name "ACQUITY APC System" Measurement conditions Column: Waters HSPgel™ HR MB-M Mobile phase: tetrahydrofuran 0.5 mL / min Sample concentration: 1 mg / mL Detector: RI detector Standard material: Polystyrene (manufactured by Aldrich, molecular weight: 370 to 2,520,000) SEC temperature: 40℃

[0046] A (meth)acrylic oligomer having a polyurethane skeleton and a polyester skeleton in its main chain and having an acryloxy group [formula (1)] or a methacryloxy group [formula (2)] at both ends of the main chain can be produced, for example, as follows: Note that the production method shown below is only one example of a method for producing the (meth)acrylic oligomer, and (meth)acrylic oligomers produced by production methods other than the production method shown below can also be used.

[0047] The polyisocyanate can be produced by reacting a diisocyanate with a polyester polyol using a general-purpose method to produce a urethane oligomer having isocyanate groups at both ends and having a polyurethane skeleton and a polyester skeleton in the main chain, and then reacting the isocyanate groups at both ends of the urethane oligomer with hydroxyl groups of a (meth)acrylate having a hydroxyl group (for example, 2-hydroxyethyl (meth)acrylate, hydroxymethyl (meth)acrylate, etc.).

[0048] The diisocyanate is not particularly limited, and examples thereof include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates.

[0049] Examples of aromatic diisocyanates include diphenylmethane diisocyanate, toluene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,3-bis(1-isocyanato-1-methylethyl)benzene, 1,4-bis(1-isocyanato-1-methylethyl)benzene, ω,ω'-diisocyanato-1,4-diethylbenzene, and urethane prepolymers having isocyanate groups at both ends.

[0050] Examples of the aliphatic diisocyanate include hexamethylene diisocyanate, tetramethylene diisocyanate, 2-methyl-pentane-1,5-diisocyanate, 3-methyl-pentane-1,5-diisocyanate, lysine diisocyanate, and trioxyethylene diisocyanate.

[0051] Examples of alicyclic diisocyanates include isophorone diisocyanate, cyclohexyl diisocyanate, hydrogenated diphenylmethane diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated tetramethylxylene diisocyanate.

[0052] Examples of polyester polyols include ester reaction products of low molecular weight diols having a molecular weight of 60 to 300 with dicarboxylic acids or reactive derivatives thereof, which have hydroxyl groups at both ends of the main chain.

[0053] The low molecular weight diol having a molecular weight of 60 to 300 is not particularly limited, and examples thereof include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butanediol, 1,6-hexanediol, 2-methyl-1,8-octanediol, nonanediol, cyclohexanedimethanol, neopentyl glycol, and 3-methyl-1,5-pentanediol.

[0054] The dicarboxylic acid is not particularly limited, and examples thereof include adipic acid, sebacic acid, succinic acid, maleic acid, phthalic acid, hexahydrophthalic acid, terephthalic acid, and the like, and anhydrides thereof.

[0055] In the (meth)acrylate polymerizable compound (A), the content of the (meth)acrylic oligomer having a polyurethane skeleton and a polyester skeleton in the main chain and having an acryloxy group [Formula (1)] or a methacryloxy group [Formula (2)] at both ends of the main chain is preferably 10% by mass or more, more preferably 15% by mass or more, more preferably 18% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. In the (meth)acrylate polymerizable compound (A), the content of the (meth)acrylic oligomer having a polyurethane skeleton and a polyester skeleton in the main chain and having an acryloxy group [Formula (1)] or a methacryloxy group [Formula (2)] at both ends of the main chain is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less. When the content of the (meth)acrylic oligomer is 10% by mass or more, the cured product of the photocurable resin composition exhibits superior adhesiveness under high temperature and high humidity conditions. When the content of the (meth)acrylic oligomer is 70% by mass or less, the cured product of the photocurable resin composition exhibits superior adhesiveness under high temperature and high humidity conditions.

[0056] In the (meth)acrylic polymerizable compound (A), the content of the polyfunctional (meth)acrylate not having a polar group is preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 15% by mass or more, and more preferably 17% by mass or more. In the (meth)acrylic polymerizable compound (A), the content of the polyfunctional (meth)acrylate not having a polar group is preferably 70% by mass or less, more preferably 60% by mass or less, more preferably 50% by mass or less, more preferably 40% by mass or less, preferably 35% by mass or less, more preferably 30% by mass or less, more preferably 27% by mass or less, and more preferably 25% by mass or less. When the content of the polyfunctional (meth)acrylate not having a polar group is 5% by mass or more, the adhesiveness of the cured product (polymer) of the photocurable resin composition under high temperature and high humidity conditions is improved. When the content of the polyfunctional (meth)acrylate is 70% by mass or less, the adhesiveness of the photocurable resin composition to an adherend under high temperature and high humidity conditions is improved.

[0057] In the (meth)acrylic polymerizable compound (A), the content of the polyfunctional (meth)acrylate having a polar group is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and more preferably 0.3% by mass or more. In the (meth)acrylic polymerizable compound (A), the content of the polyfunctional (meth)acrylate having a polar group is preferably 5% by mass or less, more preferably 4% by mass or less, and more preferably 3% by mass or less. When the content of the polyfunctional (meth)acrylate having a polar group is 0.1% by mass or more, the adhesion of the photocurable resin composition to an adherend is improved. When the content of the polyfunctional (meth)acrylate having a polar group is 5% by mass or less, the coatability of the photocurable resin composition is improved.

[0058] In the polyfunctional (meth)acrylate, examples of the polar group include a carboxyl group (-COOH), a hydroxyl group (-OH), a phosphonic acid group [-P(=O)(OH)], a phosphoric acid group [-OP(=O)(OH)], and a functional group represented by formula (6). In formula (6), *6 and *7 represent bonds and represent single bonds.

[0059] [ka]

[0060] [Photopolymerization initiator (B)] The photocurable resin composition contains a photopolymerization initiator (B). The photopolymerization initiator generates radicals upon irradiation with radiation, and radically polymerizes the (meth)acrylic polymerizable compound (A) contained in the photocurable resin composition.

[0061] The photopolymerization initiator (B) is not particularly limited as long as it can radically polymerize the (meth)acrylic polymerizable compound (A) contained in the photocurable resin composition. Examples of preferred photopolymerization initiators include α-hydroxyketone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and triazine-based photopolymerization initiators. Among these, α-hydroxyketone-based photopolymerization initiators are preferred because they have excellent compatibility with the (meth)acrylic polymerizable compound (A) and provide excellent curing properties for the photocurable resin composition. The photopolymerization initiator (B) may be used alone or in combination of two or more.

[0062] The α-hydroxyketone photopolymerization initiator is not particularly limited, and examples thereof include 1-hydroxycyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, and 2-hydroxy-2-methyl-1-phenyl-propan-1-one.

[0063] Examples of the acylphosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0064] Examples of thioxanthone-based photopolymerization initiators include 2,4-diethylthioxanthone.

[0065] Examples of the triazine-based photopolymerization initiator include 2-[2-(furan-2-yl)vinyl]-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-[2-(5-methylfuran-2-yl)vinyl]-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-[(4-methoxyphenyl)vinyl]-4,6-bis(trichloromethyl)-1,3,5-triazine, and 2-[(3,4-dimethoxyphenyl)vinyl]-4,6-bis(trichloromethyl)-1,3,5-triazine.

[0066] In the photocurable resin composition, the content of the photopolymerization initiator is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more, per 100 parts by mass of the (meth)acrylic polymerizable compound (A) contained in the photocurable resin composition. In the photocurable resin composition, the content of the photopolymerization initiator is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.0 parts by mass or less, per 100 parts by mass of the (meth)acrylic polymerizable compound (A) contained in the photocurable resin composition. When the content of the photopolymerization initiator is 0.1 parts by mass or more, the photocurability of the photocurable resin composition is improved. When the content of the photopolymerization initiator is 5.0 parts by mass or less, the molecular weight of the cured product (polymer) of the photocurable resin composition is increased, improving the cohesive force and improving the adhesion of the cured product of the photocurable resin composition to an adherend.

[0067] [Silane coupling agents (C) and (D)] The photocurable resin composition contains a silane coupling agent (C) having an SP value of less than 17.5 (hereinafter, sometimes simply referred to as "silane coupling agent (C)") and a silane coupling agent (D) having an SP value of 17.5 or more (hereinafter, sometimes simply referred to as "silane coupling agent (D)").

[0068] The silane coupling agent has a structure in which a hydrolyzable group is bonded to a silicon atom. The hydrolyzable group is not particularly limited and examples thereof include a hydrogen atom, an alkoxy group, an acyloxy group, a ketoximate group, an aminooxy group, a mercapto group, and an alkenyloxy group. An alkoxy group is preferred, and a methoxy group and an ethoxy group are more preferred, since they improve the adhesion of the cured product of the photocurable resin composition to an adherend.

[0069] The photocurable resin composition contains a silane coupling agent (C) having an SP value of less than 17.5 and a silane coupling agent (D) having an SP value of 17.5 or more. Depending on the adherend (e.g., glass, synthetic resin, etc.) to be bonded using the photocurable resin composition, either the silane coupling agent (C) or (D) will act preferentially on the adherend, while the other silane coupling agent will act preferentially on the polymer produced by polymerizing the (meth)acrylic polymerizable compound (A). As a result, the adhesive and adherend can be firmly bonded via the two types of silane coupling agents (C) and (D), and as a result, the adherend is firmly bonded by the adhesive.

[0070] The SP values ​​of the silane coupling agents (C) and (D) are values ​​calculated by the Fedors formula shown below.

[0071]

number

[0072] As described above, the SP value of a silane coupling agent is calculated based on the sum of the cohesive energy and the sum of the molecular volume of each atomic group. The sum of the cohesive energy and the sum of the molecular volume of each atomic group have been proposed by Fedors, and the SP value of a silane coupling agent can be calculated based on the proposed values. For example, the SP value of a silane coupling agent tends to be low when it has a radical polymerizable functional group in the molecule.

[0073] The radically polymerizable functional group may be any functional group capable of radically polymerizing with the (meth)acrylic polymerizable compound (A), and is preferably a vinyl group, an acryloxy group, or a methacryloxy group.

[0074] An acryloxy group is a monovalent atomic group represented by formula (1), and a methacryloxy group is a monovalent atomic group represented by formula (2). In formulas (1) and (2), *1 and *2 are bonding groups and represent single bonds.

[0075] [ka]

[0076] [ka]

[0077] First, the silane coupling agent (C) having an SP value of less than 17.5 will be explained. The silane coupling agent (C) having an SP value of less than 17.5 is not particularly limited, and examples thereof include vinyltrimethoxysilane, vinyltriethoxysilane, (3-acryloxypropyl)trimethoxysilane, (3-methacryloxypropyl)trimethoxysilane, (3-methacryloxypropyl)triethoxysilane, (3-methacryloxyoctyl)trimethoxysilane, (3-mercaptopropyl)trimethoxysilane, etc., and alkoxysilane is preferred, trialkoxysilane is more preferred, trimethoxysilane and triethoxysilane are more preferred, and vinyltriethoxysilane, (3-acryloxypropyl)trimethoxysilane and (3-methacryloxypropyl)trimethoxysilane are preferred.

[0078] The SP value of the silane coupling agent (C) is less than 17.5, preferably 17.3 or less, and more preferably 17.2 or less. The SP value of the silane coupling agent (C) is preferably 15 or more, more preferably 15.3 or more, and more preferably 15.5 or more.

[0079] The silane coupling agent (C) having an SP value of less than 17.5 preferably has a radically polymerizable functional group in the molecule. The silane coupling agent (C) having an SP value of less than 17.5 is preferably an alkoxysilane having a radically polymerizable functional group in the molecule (preferably a vinyl group, an acryloxy group, or a methacryloxy group), more preferably a trialkoxysilane having a radically polymerizable functional group in the molecule (preferably a vinyl group, an acryloxy group, or a methacryloxy group), more preferably a trimethoxysilane having a radically polymerizable functional group in the molecule (preferably a vinyl group, an acryloxy group, or a methacryloxy group), or more preferably a triethoxysilane having a radically polymerizable functional group in the molecule (preferably a vinyl group, an acryloxy group, or a methacryloxy group). The silane coupling agent (C) having an SP value of less than 17.5 is preferably a vinylalkoxysilane, methacryloxyalkylalkoxysilane, or acryloxyalkylalkoxysilane, more preferably a vinyltrialkoxysilane, methacryloxyalkyltrialkoxysilane. The alkoxy group contained in the silane coupling agent (C) having an SP value of less than 17.5 is preferably a methoxy group, an ethoxy group, a propoxy group, or a butoxy group, with a methoxy group or an ethoxy group being more preferred. When the silane coupling agent (C) having an SP value of less than 17.5 has a radically polymerizable functional group in its molecule, the silane coupling agent (C) is dispersed and incorporated into the polymer produced by polymerization of the (meth)acrylic polymerizable compound (A) during the radical polymerization reaction of the (meth)acrylic polymerizable compound (A) during curing of the photocurable resin composition. Therefore, the cured product of the photocurable resin composition exhibits uniform adhesion to the adherend overall, and the cured product (polymer) of the photocurable resin composition exhibits excellent adhesion to the adherend under high temperature and high humidity conditions.

[0080] Furthermore, since the silane coupling agent (C) is incorporated into the polymer, the silane coupling agent (C) is not excessively unevenly distributed on the adherend, and is maintained in an appropriately dispersed state in the cured product (polymer) of the photocurable resin composition for a long period of time. As a result, the cured product of the photocurable resin composition can maintain overall uniform adhesion to the adherend under high temperature and high humidity conditions for a long period of time, and the cured product of the photocurable resin composition can maintain excellent adhesion to the adherend under high temperature and high humidity conditions for a long period of time.

[0081] The silane coupling agent (C) preferably has a methacryloxy group or an acryloxy group as the radical polymerizable functional group, and more preferably has a methacryloxy group. When the silane coupling agent (C) has a (meth)acryloxy group as the radical polymerizable functional group, it is incorporated in a more well-dispersed state into the cured product (polymer) of the photocurable resin composition in the copolymerization reaction with the (meth)acrylic polymerizable compound (A), and the cured product of the photocurable resin composition exhibits more uniform overall adhesion to the adherend under high temperature and high humidity conditions, and the cured product (polymer) of the photocurable resin composition exhibits even better adhesion to the adherend under high temperature and high humidity conditions.

[0082] Next, the silane coupling agent (D) having an SP value of 17.5 or more will be described. The silane coupling agent (D) having an SP value of 17.5 or more is not particularly limited, and examples thereof include (3-glycidyloxypropyl)triethoxysilane, (3-glycidyloxypropyl)trimethoxysilane, (3-glycidyloxyoctyl)trimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane. Since the adhesiveness of the cured product of the photocurable resin composition to the adherend under high temperature and high humidity conditions is improved, (3-glycidyloxypropyl)triethoxysilane and (3-glycidyloxypropyl)trimethoxysilane are preferred.

[0083] The SP value of the silane coupling agent (D) is 17.5 or more, preferably 17.55 or more, and more preferably 17.6 or more. The SP value of the silane coupling agent (D) is preferably 20 or less, more preferably 19.5 or less, more preferably 19 or less, more preferably 18 or less, more preferably 17.9 or less, and more preferably 17.8 or less.

[0084] The silane coupling agent (D) having an SP value of 17.5 or more preferably has an epoxy group, and more preferably has a glycidyl group, since it improves the adhesion of the cured product of the photocurable resin composition to an adherend under high temperature and high humidity conditions without impairing the photocurability of the photocurable resin composition.

[0085] When the silane coupling agent (D) having an SP value of 17.5 or more has a glycidyl group, the silane coupling agent (D) preferably has a structure in which an alkyl group is bonded to a silicon atom and the hydrogen bonded to the carbon atom of the alkyl group is substituted with a glycidyloxy group (glycidyloxyalkylsilane), a structure in which an alkyl group and an alkoxy group (preferably, a methoxy group or an ethoxy group) are bonded to a silicon atom and the hydrogen bonded to the carbon atom of the alkyl group is substituted with a glycidyloxy group (glycidyloxyalkylalkoxysilane), or a structure in which one alkyl group and three alkoxy groups (preferably, a methoxy group or an ethoxy group) are bonded to a silicon atom and the hydrogen bonded to the carbon atom of the alkyl group is substituted with a glycidyloxy group (glycidyloxyalkyltrialkoxysilane). The number of carbon atoms in the alkyl group is preferably 1 to 12, more preferably 2 to 10. When the number of carbon atoms in the alkyl group is within the above range, the cured product of the photocurable resin composition has excellent adhesion to adherends under high temperature and high humidity conditions.

[0086] The glycidyloxy group has the following structure (3): *3 is a bond and means a single bond.

[0087] [ka]

[0088] It is preferable that the silane coupling agent (D) having an SP value of 17.5 or more does not have a radically polymerizable functional group in the molecule. If the silane coupling agent (D) does not have a radically polymerizable functional group in the molecule, the silane coupling agent (D) will not be incorporated into the polymer produced by radical polymerization of the (meth)acrylic polymerizable compound (A) in the radical polymerization reaction during curing of the photocurable resin composition, and will exist in a free state in the cured product (polymer) of the photocurable resin composition. Therefore, the silane coupling agent (D) can migrate within the cured product of the photocurable resin composition as needed to improve its effect on the adherend, thereby improving the adhesion of the cured product of the photocurable resin composition to the adherend under high temperature and high humidity conditions.

[0089] Among the silane coupling agents (C) and (D), when the silane coupling agent (C) having an SP value of less than 17.5 has a radically polymerizable functional group in the molecule, while the silane coupling agent (D) having an SP value of 17.5 or more does not have a radically polymerizable functional group in the molecule, the silane coupling agent (C) having an SP value of less than 17.5 can be incorporated into the cured product (polymer) of the photocurable resin composition, allowing the silane coupling agent (C) to be appropriately dispersed in the cured product of the photocurable resin composition, and the silane coupling agent (D) having an SP value of 17.5 or more to exist in a free state in the cured product of the photocurable resin composition.

[0090] Therefore, the silane coupling agent (C) is incorporated into the polymer, restricting excessive movement, while the silane coupling agent (D) is allowed to be mobile within the polymer of the photocurable resin composition, and while preventing excessive uneven distribution of the silane coupling agents (C) and (D), the silane coupling agents (C) and (D) move appropriately depending on the adherend, allowing the silane coupling agent to act uniformly on the adherend, and the cured product of the photocurable resin composition exhibits excellent adhesion to the adherend under high temperature and high humidity conditions.

[0091] When the silane coupling agent (C) having an SP value of less than 17.5 has a radically polymerizable functional group in its molecule, while the silane coupling agent (D) having an SP value of 17.5 or more does not have a radically polymerizable functional group in its molecule, if the adherend is glass, the silane coupling agent (D) having a high SP value that is in a free state in the cured product of the photocurable resin composition can act effectively on the glass because glass has a high SP value, and the photocurable resin composition can exhibit excellent adhesion, particularly to glass, under high temperature and high humidity conditions.

[0092] The content of the silane coupling agent (C) in the photocurable resin composition is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the (meth)acrylic polymerizable compound (A). The content of the silane coupling agent (C) in the photocurable resin composition is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of the (meth)acrylic polymerizable compound (A). When the content of the silane coupling agent (C) is 0.5 parts by mass or more, the silane coupling agent can be uniformly dispersed throughout the cured product of the photocurable resin composition or at the interface with the adherend, and the cured product of the photocurable resin composition exhibits excellent adhesion to the adherend under high temperature and high humidity conditions. When the content of the silane coupling agent (C) is 10 parts by mass or less, the cohesive strength of the cured product (polymer) of the photocurable resin composition can be improved, thereby improving adhesion to the adherend.

[0093] The content of the silane coupling agent (D) in the photocurable resin composition is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and more preferably 0.5 parts by mass or more, per 100 parts by mass of the (meth)acrylic polymerizable compound. The content of the silane coupling agent (D) in the photocurable resin composition is preferably 7 parts by mass or less, more preferably 6 parts by mass or less, more preferably 5 parts by mass or less, and more preferably 4 parts by mass or less, per 100 parts by mass of the (meth)acrylic polymerizable compound. When the content of the silane coupling agent (D) is 0.1 parts by mass or more, the cured product of the photocurable resin composition exhibits excellent adhesion to the adherend under high temperature and high humidity conditions. When the content of the silane coupling agent (D) is 7 parts by mass or less, the cohesive strength of the cured product (polymer) of the photocurable resin composition can be improved, thereby improving adhesion to the adherend.

[0094] The total content of the silane coupling agents (C) and (D) in the photocurable resin composition is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and more preferably 3 parts by mass or more, per 100 parts by mass of the (meth)acrylic polymerizable compound (A). The total content of the silane coupling agents (C) and (D) in the photocurable resin composition is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and more preferably 8 parts by mass or less, per 100 parts by mass of the (meth)acrylic polymerizable compound (A). When the total content of the silane coupling agents (C) and (D) is 1 part by mass or more, the adhesiveness of the cured product of the photocurable resin composition to the adherend under high temperature and high humidity conditions is improved. When the total content of the silane coupling agents (C) and (D) is 15 parts by mass or less, the cohesive strength of the cured product (polymer) of the photocurable resin composition is improved, thereby improving the adhesiveness to the adherend.

[0095] In the photocurable resin composition, the mass ratio of the content of the silane coupling agent (C) having an SP value of less than 17.5 to the content of the silane coupling agent (D) having an SP value of 17.5 or more [silane coupling agent (C) having an SP value of less than 17.5 / silane coupling agent (D) having an SP value of 17.5 or more] (hereinafter sometimes referred to as the "silane coupling agent ratio") is preferably 0.5 or more, more preferably 1 or more, more preferably 2 or more, more preferably 2.3 or more, more preferably 3 or more, and more preferably 4 or more. In the photocurable resin composition, the mass ratio of the content of the silane coupling agent (C) having an SP value of less than 17.5 to the content of the silane coupling agent (D) having an SP value of 17.5 or more [silane coupling agent (C) having an SP value of less than 17.5 / silane coupling agent (D) having an SP value of 17.5 or more] is preferably 25 or less, more preferably 24 or less, more preferably 20 or less, more preferably 17 or less, more preferably 13 or less, more preferably 11 or less, more preferably 10 or less, more preferably 9 or less, and more preferably 7 or less. When the silane coupling agent ratio is 0.5 or more, the adhesion of the cured product of the photocurable resin composition to an adherend under high temperature and high humidity conditions is improved. When the silane coupling agent ratio is 25 or less, the adhesion of the cured product of the photocurable resin composition to an adherend under high temperature and high humidity conditions is improved.

[0096] [Additives] The photocurable resin composition may contain a thixotropic agent, an adhesion-imparting resin, a plasticizer, non-thermally expandable fine particles, a dye, a pigment, a flame retardant, a surfactant, and the like, within the range that does not impair the physical properties of the composition.

[0097] [Photocurable resin composition] The method for producing the photocurable resin composition is not particularly limited, and the photocurable resin composition can be produced, for example, by uniformly mixing the (meth)acrylic polymerizable compound (A), the photopolymerization initiator (B), the silane coupling agent (C), the silane coupling agent (D), and additives contained as needed in a general manner, preferably under reduced pressure.

[0098] The photocurable resin composition contains as essential components a (meth)acrylic polymerizable compound (A), a photopolymerization initiator (B), a silane coupling agent (C) having an SP value of less than 17.5, and a silane coupling agent (D) having an SP value of 17.5 or more, and does not need to contain any components that would increase the viscosity of the photocurable resin composition. Therefore, the viscosity can be kept low, the photocurable resin composition can be applied to the surface of an adherend in a thin film thickness, and the adherend can be bonded and integrated with the thin cured product of the photocurable resin composition.

[0099] Furthermore, since the photocurable resin composition can be applied to the surface of an adherend in a thin film thickness, the coating of the photocurable resin composition can be irradiated with radiation sufficiently to the inside, allowing the photoradical polymerization reaction to proceed smoothly and sufficiently, thereby producing a cured product with excellent adhesive properties even under high temperature and high humidity conditions.

[0100] The viscosity of the photocurable resin composition at 25°C is preferably 1 mPa·s or more, more preferably 2 mPa·s or more, and more preferably 3 mPa·s or more. The viscosity of the photocurable resin composition at 25°C is preferably 5000 mPa·s or less, more preferably 4000 mPa·s or less, more preferably 3000 mPa·s or less, more preferably 1000 mPa·s or less, more preferably 900 mPa·s or less, more preferably 800 mPa·s or less, more preferably 700 mPa·s or less, more preferably 600 mPa·s or less, more preferably 500 mPa·s or less, more preferably 400 mPa·s or less, more preferably 300 mPa·s or less, more preferably 200 mPa·s or less, more preferably 100 mPa·s or less, and more preferably 50 mPa·s or less. When the viscosity of the photocurable resin composition at 25°C is 1 mPa·s or more, the adhesiveness of the cured product of the photocurable resin composition to an adherend is improved.When the viscosity of the photocurable resin composition at 25°C is 5000 mPa·s or less, the coatability of the photocurable resin composition to an adherend surface is improved.

[0101] The viscosity of the photocurable resin composition is measured in accordance with JIS K6833 using a Brookfield viscometer and a low-viscosity measurement spindle (a spindle capable of measuring 20 mPa·s or less) at 25°C, 50% relative humidity, and 50 rpm. The low-viscosity measurement spindle may be, for example, one commercially available from Eiko Instruments Co., Ltd. under the trade name "ULA."

[0102] [Method for bonding adherends using photocurable resin composition] Photocurable resin compositions are used to bond and integrate adherends together. The adherends are not particularly limited, and examples thereof include thin-layer glass, optical glass, prisms, lenses, silicon wafers, semiconductor mounting components, and synthetic resin molded products (e.g., synthetic resin sheets). The photocurable resin composition can be suitably used as an optical adhesive for bonding and integrating optical adherends. The photocurable resin composition can be particularly suitably used for bonding and integrating optical adherends such as thin-layer glass, optical glass, prisms, and lenses. The adherends may be of the same type or different types.

[0103] The procedure for bonding and integrating adherends using a photocurable resin composition will now be described. First, adherends are stacked together with the photocurable resin composition between opposing surfaces of the adherends to produce a laminate (lamination step). Three or more adherends may also be stacked together with the photocurable resin composition between opposing surfaces of the adherends to produce a laminate.

[0104] In the lamination process, when producing a laminate, the photocurable resin composition can be applied in a thin film thickness, so the thickness of the entire laminate can be made thin, and the finished product obtained using the photocurable resin composition can be made smaller.

[0105] Since the photocurable resin composition is a one-component type, the production of a laminate does not require the complicated operation of mixing two components, and the laminate can be easily produced.

[0106] Next, the entire laminate obtained is irradiated with radiation from the stacking direction of the laminate to cure the photocurable resin composition interposed between the opposing surfaces of the adherends constituting the laminate, thereby producing a cured product (polymer) (curing step).This cured product can bond and integrate the adherends together.

[0107] The photocurable resin composition can be applied to the surface of an adherend in a thin film thickness, and therefore the photocurable resin composition applied to the surface of the adherend can be cured sufficiently and reliably to exhibit excellent adhesion.

[0108] The peak wavelength of the radiation is preferably 500 nm or less, as this provides excellent curing properties for the photocurable resin composition. The radiation is irradiated in the lamination direction (thickness direction) of the laminate, and the radiation is preferably light with a wavelength of 320 nm or more. By using radiation with a wavelength of 320 nm or more, absorption of the radiation by the optical glass can be largely prevented, and even when multiple photocurable resin composition layers are present, the radiation can be sufficiently transmitted to all of the photocurable resin composition layers. Furthermore, the photopolymerization initiator (B) contained in the photocurable resin composition effectively absorbs the radiation, allowing the radical polymerization of the (meth)acrylic polymerizable compound (A) and, if necessary, the silane coupling agent contained in the photocurable resin composition to proceed smoothly.

[0109] Furthermore, even if multiple layers of photocurable resin composition are present, the radiation does not need to be applied to the laminate for each layer of the photocurable resin composition. After the laminate is produced, radiation can be applied to the entire thickness of the laminate in the stacking direction of the laminate, thereby irradiating all of the photocurable resin composition constituting the laminate with radiation and reliably curing it in a short period of time, thereby bonding and integrating the adherends together.

[0110] Furthermore, the cured product of the photocurable resin composition that bonds and integrates the adherends maintains excellent adhesive properties even under high temperature and high humidity conditions, so that the bonded and integrated state of the adherends can be reliably maintained even in harsh environments such as the interior of an automobile. [Example]

[0111] The present invention will be described in more detail below using examples, but the present invention is not limited thereto. Specific numerical values ​​of blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the upper limit values ​​(numeric values ​​defined as "equal to or less than") or lower limit values ​​(numeric values ​​defined as "equal to or greater than") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the "Summary of the Invention."

[0112] The following compounds were used in the examples and comparative examples.

[0113] [(Meth)acrylic polymerizable compound (A)] [Monofunctional (meth)acrylic polymerizable compounds] Methacrylic acid (Monofunctional (meth)acrylate having an aromatic ring) Phenoxyethyl acrylate (Monofunctional (meth)acrylate having a saturated aliphatic ring structure) Dicyclopentanyl methacrylate Isobornyl acrylate

[0114] [Polyfunctional (meth)acrylic polymerizable compounds] (Polyfunctional (meth)acrylate without polar group) 1,6-Hexanediol dimethacrylate Multifunctional acrylic oligomer 1 (manufactured by Nippon Kayaku Co., Ltd., trade name "UX-4101", having a polyurethane skeleton and a polyester skeleton in the main chain, having acryloxy groups [formula (1)] at both ends of the main chain, having no polar groups in the molecule, weight average molecular weight: 6500) Multifunctional acrylic oligomer 2 (manufactured by Daicel-Allnex Corporation, trade name "EBECRYL8411", having a polyurethane skeleton and a polyester skeleton in the main chain, having acryloxy groups [formula (1)] at both ends of the main chain, having no polar groups in the molecule, weight average molecular weight: 12,000) (Polyfunctional (meth)acrylate having a polar group) Bis(2-methacryloxyethyl) acid phosphate (Kyoeisha Chemical Co., Ltd., product name "Light Ester P-2M")

[0115] [Photopolymerization initiator (B)] 1-Hydroxycyclohexyl phenyl ketone

[0116] [Silane coupling agent (C)] Vinyltriethoxysilane (SP value: 15.88, radical polymerizable functional group: vinyl group) (3-Methacryloxypropyl)trimethoxysilane (SP value: 17.05, radical polymerizable functional group: methacryloxy group) (3-acryloxypropyl)trimethoxysilane (SP value: 17.28, radical polymerizable functional group: methacryloxy group) Hexyltrimethoxysilane (SP value: 15.88, radical polymerizable functional group: none)

[0117] [Silane coupling agent (D)] (3-glycidyloxypropyl)triethoxysilane (SP value: 17.71, radical polymerizable functional group: none, contains glycidyl group) (8-glycidyloxyoctyl)trimethoxysilane (SP value: 17.65, radical polymerizable functional group: none, contains glycidyl group)

[0118] (Example 1 17 , Comparative Example 1~ 6 ) The (meth)acrylic polymerizable compound (A), silane coupling agent (C) and silane coupling agent (D) in the predetermined amounts shown in Tables 1 to 3 were respectively supplied to a reaction vessel and mixed uniformly to prepare a mixed solution.

[0119] Next, a predetermined amount of photopolymerization initiator (B) shown in Tables 1 to 3 was supplied to the mixed liquid, and the mixture was mixed until the photopolymerization initiator (B) was completely dissolved in the mixed liquid, thereby obtaining a photocurable resin composition.

[0120] The viscosity of the obtained photocurable resin composition before curing at 25° C. was measured in the same manner as described above, and the results are shown in Tables 1 to 3.

[0121] The initial adhesive strength and high-temperature, high-humidity adhesive strength of the obtained photocurable resin composition, as well as the fracture morphology under the measurement conditions for the initial adhesive strength and the adhesive strength at high temperature and high humidity, were measured in the following manner, and the results are shown in Tables 1 to 3.

[0122] [Initial adhesive strength] Two rectangular parallelepiped glass plates 1 and 2, each measuring 50 mm long, 25 mm wide, and 5 mm thick, were prepared. The entire surfaces of the two glass plates were washed with ethanol and then dried.

[0123] As shown in Figures 1 and 2, one glass sheet 1 was placed on a horizontal support surface 3, and the long edge of the other glass sheet 2 was overlapped on the long edge of the glass sheet 1. The overlap width between the edges of the two glass sheets 1 and 2 was 12.5 mm. A photocurable resin composition 5 was interposed between the long edge of the two glass sheets 1 and 2, and the photocurable resin composition 5 was filled across the entire lateral length between the opposing surfaces of the long edge of the two glass sheets 1 and 2. The photocurable resin composition 5 measured 25 mm long, 12.5 mm wide, and 0.01 mm thick. A supporting glass sheet 4 was placed in the gap between the upper overlapping glass sheet and the support surface, and the upper glass sheet 2 was supported by the supporting glass sheet 4.

[0124] The photocurable resin composition 5 placed between the two glass sheets 1 and 2 was irradiated with ultraviolet light having a peak wavelength of 360 nm at an illuminance of 2 mW / cm using an ultraviolet lamp (trade name "FL20S·BL" manufactured by Toshiba Lighting & Technology Corporation). 2 The photocurable resin composition 5 was cured by irradiating the two glass plates with ultraviolet light for 10 minutes to produce a cured body in which the two glass plates were laminated together via the cured product of the photocurable resin composition. The ultraviolet lamp was positioned vertically above the overlapping portion of the two glass plates and at a height of 80 mm from the placement surface.

[0125] The resulting cured product was subjected to a three-point bending test using a desktop precision universal testing machine (Shimadzu Corporation, product name "Autograph AGS-100NX"), where the overlapping portion of the two glass plates was pressed at a pressing speed of 10 mm / min, and the maximum strength obtained was taken as the measured strength (N), and the adhesive strength was calculated using the following formula: The ambient environment during the strength measurement was 25°C and relative humidity 50%.

[0126] Initial adhesive strength (MPa) =Measurement strength (N) / [0.025(m)×0.0125(m)×10 -6 ]

[0127] [High temperature and high humidity adhesive strength] A cured product was prepared in the same manner as for the initial adhesive strength test, and then left for 48 hours in a high-temperature, high-humidity atmosphere of 120°C, 0.1 MPa, and 100% relative humidity.

[0128] The cured product was then removed from the high-temperature, high-humidity atmosphere and placed in a 25°C, 50% relative humidity atmosphere for 24 hours. After this, the high-temperature, high-humidity adhesive strength of the resulting cured product was measured in the same manner as for the initial adhesive strength.

[0129] The adhesive strength retention rate (%) was calculated based on the following formula and is shown in Tables 1 to 3. Adhesive strength maintenance rate (%) = 100 × high temperature and high humidity adhesive strength / initial adhesive strength

[0130] [Peeling form] After measuring the initial adhesive strength and the high-temperature, high-humidity adhesive strength, the cured product was visually observed at the portion where the two glass plates were laminated together via the cured product of the photocurable resin composition, and evaluated based on the following criteria. Material failure: The glass plate was broken. Interfacial fracture: fracture occurred at the interface between the glass plate and the cured product of the photocurable resin composition.

[0131] [Table 1]

[0132] [Table 2]

[0133] [Table 3] [Industrial Applicability]

[0134] The photocurable resin composition of the present invention can firmly bond and integrate adherends together even under high temperature and high humidity conditions, and can therefore be suitably used for bonding and integrating adherends together in harsh environments such as the interior of an automobile.

[0135] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to Japanese Patent Application No. 2022-171960, filed October 27, 2022, and Japanese Patent Application No. 2023-101972, filed June 21, 2023, the disclosures of which are incorporated herein by reference in their entireties. [Explanation of symbols]

[0136] 1. Plate glass 2. Plate glass 3. Placement surface 4 Supporting glass plate 5 Photocurable resin composition

Claims

1. The composition contains a (meth)acrylic polymerizable compound (A), a photopolymerization initiator (B), a silane coupling agent (C) having an SP value of less than 17.5, and a silane coupling agent (D) having an SP value of 17.5 or more, The (meth)acrylic polymerizable compound (A) contains 30 to 90% by mass of a monofunctional (meth)acrylate, 5 to 20% by mass of (meth)acrylic acid, and 5 to 65% by mass of a polyfunctional (meth)acrylate, The silane coupling agent (C) having an SP value of less than 17.5 has a radical polymerizable functional group in the molecule, the silane coupling agent (D) having an SP value of 17.5 or more is contained in an amount of 0.5 to 7 parts by mass per 100 parts by mass of the (meth)acrylic polymerizable compound (A), the mass ratio of the content of the silane coupling agent (C) having an SP value of less than 17.5 to the content of the silane coupling agent (D) having an SP value of 17.5 or more [silane coupling agent (C) having an SP value of less than 17.5 / silane coupling agent (D) having an SP value of 17.5 or more] is 2 to 25, The photocurable resin composition is characterized in that the silane coupling agent (D) having an SP value of 17.5 or more has an epoxy group.

2. 2. The photocurable resin composition according to claim 1, wherein the silane coupling agent (D) having an SP value of 17.5 or more has a glycidyl group.

3. 3. The photocurable resin composition according to claim 1, wherein the viscosity at 25° C. is 1 to 5000 mPa·s.

4. An optical adhesive comprising the photocurable resin composition according to claim 1 or 2.

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